Page 106 - Soil Degradation, Conservation and Remediation

3.4 Control of Water Erosion 93

Step 9 Practicing crop rotation: A good way of rotating is to plant cereals such
as corn or upland rice, tubers, and other crops on strips where legumes
were planted previously.
Step 10 Building green terraces: To enrich the soil and effectively control erosion,

organic materials such as straw, stalks, twigs, branches and leaves, and
also rocks and stones are piled at the base of the rows of nitrogen- fi xing
trees. By the passage of time, permanent effective terraces will be formed.
SALT has been applied in many other countries with variable success. However,
it may be an alternative to shifting cultivation in degraded hilly lands.

3.4.9 Agroforestry

Agroforestry is a system of growing agricultural or horticultural crops or/and rearing
livestock along with trees simultaneously or sequentially in the same piece of land. The
objectives of agroforestry include conserving soil, recycling nutrients, and enhancing
crop yields, while producing fuelwood, fodder, grain, fruit, and timber (Nair 1989 ). It
involves the integration of trees, plants, and animals in conservative, long-term, pro-
ductive systems. The positive interactions among all these components are exploited in
carefully designed sustainable agroforestry systems (Sanchez 1995 ) by (i) multiple use
of land; (ii) improved utilization of land, labor, and resources; (iii) protection and
improvement of soil by reducing erosion and providing soil organic matter; (iv) pro-
duction of diverse food crops such as fruits, nuts, grains, and seeds; (v) production of
feed for farm animals; (vi) long-term production of tree products; and (vii) enhanced
productivity and net economic returns. In agroforestry trees are used in these ways: (i)
individual trees in home gardens, around houses, paths, and public places; (ii) dis-
persed trees in cropland and pastures; (iii) rows of trees with crops between; (iv) strips
of trees along contours or waterways; (v) living fences and borderlines; and (vi) wind-
breaks. There are two functionally different types of agroforestry systems: simultane-
ous and sequential (ICRAF 1994 ). In simultaneous agroforestry system, the tree and
the crop components grow at the same time and in close enough proximity for interac-
tions to occur. Examples of this type are alley cropping, contour buffering, border
planting, and different silvopastoral systems. In sequential agroforestry systems, the
maximum growth rates of the crop and the tree components occur at different times
even though both components may have been planted at the same time and are in close
proximity. Examples of this type are shifting cultivation, improved fallows, taungya,
and some multistrata systems.

3.4.10 Alley Cropping

In alley cropping, crops (grains, forages, vegetables, etc.) are grown between tree
rows spaced widely enough to accommodate the mature size of the trees without